U.S. patent application number 13/119928 was filed with the patent office on 2011-07-28 for compensating frequency mismatch in gyroscopes.
This patent application is currently assigned to Hewlett-Packard Development Company, L.P.. Invention is credited to Robert G. Walmsley, Wenhua Zhang.
Application Number | 20110179866 13/119928 |
Document ID | / |
Family ID | 42129122 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110179866 |
Kind Code |
A1 |
Zhang; Wenhua ; et
al. |
July 28, 2011 |
COMPENSATING FREQUENCY MISMATCH IN GYROSCOPES
Abstract
Gyroscopes that can compensate frequency mismatch are provided.
In this regard, a representative gyroscope, among others, includes
a top substrate including an outermost structure, a first driving
structure and a first sensing structure. The first driving
structure and the first sensing structure are disposed within the
outermost structure. The first driving structure and the first
sensing structure include a first driving electrode and a first
sensing electrode that are disposed on a bottom surface of the
first driving structure and first sensing structure, respectively.
A portion of the mass on the top surface of the first sensing
structure is removed. The gyroscope further includes a bottom
substrate that is disposed below the top substrate. The bottom
substrate includes a second driving electrode and a second sensing
electrode that are disposed on a top surface of the bottom
substrate and below the first driving electrode and the first
sensing electrode.
Inventors: |
Zhang; Wenhua; (Sunnyvale,
CA) ; Walmsley; Robert G.; (Palo Alto, CA) |
Assignee: |
Hewlett-Packard Development
Company, L.P.
Houston
TX
|
Family ID: |
42129122 |
Appl. No.: |
13/119928 |
Filed: |
October 31, 2008 |
PCT Filed: |
October 31, 2008 |
PCT NO: |
PCT/US2008/081985 |
371 Date: |
March 18, 2011 |
Current U.S.
Class: |
73/504.08 ;
29/592.1 |
Current CPC
Class: |
G01C 19/5755 20130101;
Y10T 29/49002 20150115; G01C 19/574 20130101 |
Class at
Publication: |
73/504.08 ;
29/592.1 |
International
Class: |
G01C 19/02 20060101
G01C019/02; H05K 13/00 20060101 H05K013/00 |
Claims
1. A gyroscope that compensates frequency mismatch comprising: a
top substrate including an outermost structure, a first driving
structure and a first sensing structure, the first driving
structure and the first sensing structure being disposed within the
outermost structure, the outermost structure being open and
enclosed, the first driving structure and the first sensing
structure including a first driving electrode and a first sensing
electrode that are disposed on a bottom surface of the first
driving structure and first sensing structure, respectively, a
portion of the mass on the top surface of the first sensing
structure being removed; and a bottom substrate that is disposed
below the top substrate, the bottom substrate including a second
driving electrode and a second sensing electrode that are disposed
on a top surface of the bottom substrate and below the first
driving electrode and the first sensing electrode.
2. The gyroscope as defined in claim 1, wherein a portion of the
mass at a certain mass removal area on the top surface of the first
driving structure has been removed.
3. The gyroscope as defined in claim 2, wherein the mass removal
area that is on the top surface of the first driving structure is
placed close to the center of the gyroscope.
4. The gyroscope as defined in claim 3, wherein the amount of the
area and the location of the area depend on the device geometric
parameters.
5. The gyroscope as defined in claim 2, wherein the removal of mass
at the mass removal area on the top surface of the first driving
structure changes the frequency of the driving structures to match
the frequency of the first sensing structure.
6. The gyroscope as defined in claim 1, wherein the outermost
structure has a octagon shape.
7. The gyroscope as defined in claim 6, further comprising second,
third, and fourth driving structures and second, third, and fourth
sensing structures, all of which are disposed with the outermost
structure, the first, second, third, and fourth sensing structures
being disposed at the top left, top right, bottom right, and bottom
left, respectively, the first driving structure being disposed
between the first sensing structure and the second sensing
structure, the second driving structure being disposed between the
second sensing structure and the third sensing structure, the third
driving structure being disposed between the third sensing
structure and the fourth sensing structure, the fourth driving
structure being disposed between the first sensing structure and
the fourth sensing structure, the first driving structure being
further disposed opposite from the third driving structure, the
second driving structure being further disposed opposite from the
fourth driving structure.
8. The gyroscope as defined in claim 7, wherein a portion of the
mass at certain mass removal areas on the top surfaces of the
first, second, third, and fourth driving structures is removed.
9. The gyroscope as defined in claim 8, wherein the mass removal
areas on the top surfaces of the first, second, third, and fourth
driving structures are close to the center of the gyroscope.
10. A method for making a gyroscope that can compensate for
frequency mismatch comprising: providing a top substrate and a
bottom substrate, the top substrate including an outermost
structure, a first driving structure and a first sensing structure,
the first driving structure and the first sensing structure being
disposed within the outermost structure, the outermost structure
being open and enclosed, the first driving structure and the first
sensing structure including a first driving electrode and a first
sensing electrode that are disposed on a bottom surface of the
first driving structure and the first sensing structure,
respectively; and removing a portion of the mass on the top surface
of the first sensing structure.
11. The method as defined in claim 10, wherein removing the portion
of the mass on the top surface of the first sensing structure is
accomplished at a certain mass removal area.
12. The method as defined in claim 11, further comprising placing
the mass removal area that is on the top surface of the first
driving structure close to the center of the gyroscope.
13. The method as defined in claim 11, further comprising changing
the frequency of the first driving structure to match the frequency
of the first sensing structure due to removing the mass at the mass
removal area on the top surface of the first driving structure.
14. A gyroscope that compensates frequency mismatch comprising: a
top substrate including an outermost structure, a first driving
structure and a first sensing structure, the first driving
structure and the first sensing structure being disposed within the
outermost structure, the outermost structure being open and
enclosed, the first driving structure and the first sensing
structure including a first driving electrode and a first sensing
electrode that are disposed on a bottom surface of the first
driving structure and the first sensing structure, respectively, a
portion of the mass on the top surfaces of the first sensing
structure and the first driving structure being removed; and a
bottom substrate that is disposed below the top substrate, the
bottom substrate including a second driving electrode and a second
sensing electrode that are disposed on a top surface of the bottom
substrate and below the first driving electrode and the first
sensing electrode.
15. The gyroscope as defined in claim 14, wherein the mass removal
area on the top surface of the first driving structure is close to
the center of the gyroscope, the amount of the area and the
location of the area depending on the device geometric parameters,
the removal of mass at the mass removal area on the top surface of
the first driving structure changing the frequency of the driving
structures to match the frequency of the first sensing structure.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to gyroscopes, and more
particularly, the disclosure relates to compensating frequency
mismatch in microelectromechanical systems (MEMS) gyroscopes.
BACKGROUND
[0002] Gyroscopes are devices that measure or maintain orientation
based on principles of angular momentum. Gyroscopes can be used in
many applications, such as, vehicle stability control, rollover
detection, navigation, load leveling/suspension control, computer
input devices, handheld computing devices, game controllers,
navigation of autonomous guided vehicles, etc. Fabrication
imperfections of the gyroscopes typically result in an oscillation
frequency mismatch between two vibrating modes. These fabrication
imperfections decrease the performance of the gyroscopes and may
cause erroneous output.
SUMMARY
[0003] Gyroscopes that can compensate for oscillation frequency
mismatch are provided. In this regard, a representative gyroscope,
among others, includes a top substrate including an outermost
structure, a first driving structure and a first sensing structure.
The first driving structure and the first sensing structure are
disposed within the outermost structure. The first driving
structure and the first sensing structure include a first driving
electrode and a first sensing electrode that are disposed on a
bottom surface of the first driving structure and the first sensing
structure, respectively. A portion of the mass on the top surface
of the first sensing structure is removed.
[0004] The gyroscope further includes a bottom substrate that is
disposed below the top substrate. The bottom substrate includes a
second driving electrode and a second sensing electrode that are
disposed on a top surface of the bottom substrate and below the
first driving electrode and the first sensing electrode.
[0005] The present invention can also be viewed as providing
methods for making a gyroscope that can compensate for frequency
mismatch. In this regard, one embodiment of such a method, among
others, can be broadly summarized by the following steps: providing
a top substrate and a bottom substrate, as described above, and
removing a portion of the mass on the top surface of a first
sensing structure of the top substrate. The removal of the mass can
be accomplished at a certain mass removal area. The method further
includes placing the mass removal area that is on the top surface
of the first driving structure close to the center of the
gyroscope. Other systems, methods, features, and advantages of the
present invention will be or become apparent to one with skill in
the art upon examination of the following drawings and detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Many aspects of the disclosure can be better understood with
reference to the following drawings. The components in the drawings
are not necessarily to scale, emphasis instead being placed upon
clearly illustrating the principles of the present disclosure.
Moreover, in the drawings, like reference numerals designate
corresponding parts throughout the several views.
[0007] FIG. 1 is a side view of an embodiment of surface electrodes
that can be used in a gyroscope.
[0008] FIG. 2 is a schematic drawing of an embodiment of a
gyroscope, such as that shown in FIG. 1.
[0009] FIG. 3 is a top view of yet another embodiment of a
gyroscope, such as that shown in FIG. 2, that can compensate for
frequency mismatch.
[0010] FIG. 4 is a flow diagram that illustrates an embodiment of a
method for making a gyroscope, such as that shown in FIG. 2, that
can compensate for frequency mismatch.
DETAILED DESCRIPTION
[0011] Exemplary systems are first discussed with reference to the
figures. Although these systems are described in detail, they are
provided for purposes of illustration only and various
modifications are feasible. After the exemplary systems are
described, examples of flow diagrams of the systems are provided to
explain the manner in which frequency mismatch in a gyroscope can
be compensated. The disclosure focuses on controllable mode
frequency match in microelectromechanical systems (MEMS) gyroscopes
where surface electrode technology is used.
[0012] FIG. 1 is a side view of an embodiment of surface electrodes
100 that can be used in a gyroscope. In general, electrodes 115 are
attached to opposite substrates 105, 110 facing each other.
Electrostatic force from substrates 105, 110 can be used to move
the electrodes 115 on the opposite of and attached to the
substrates 105, 110, respectively, while capacitance that changes
between the electrodes 115 during motion provides capacitance
signal to detect the motion. On each of the substrates 105, 110,
the electrodes 115 may form several groups depending on specific
applications, so that a voltage pattern can be applied to the
electrodes 115 and the pattern can alternate periodically in the
moving direction.
[0013] FIG. 2 is a schematic drawing of an embodiment of a
gyroscope 200, such as that shown in FIG. 1. The gyroscope 200
includes a top substrate 202 and a bottom substrate 205. The top
substrate 202 includes an outermost structure 210, one or more
sensing structures 215, and one or more driving structures 225. In
this example, the outermost structure 210 and the sensing structure
215 are open and enclosed similar to that of a window frame. The
outermost structure 210 is generally fixed and does not move. The
sensing structure 215 and the driving structure 225 are disposed
within and supported to the outermost structure 210 and the sensing
structure 215 using microbeams 350A-H (FIG. 3), respectively.
[0014] The sensing structure 215 includes first sensing electrodes
232 that are disposed on a bottom surface 236 of the sensing
structure 215 and aligned parallel to at least one side wall 238,
239 of the sensing structure 215. In this example, the first
sensing electrodes 232 are disposed at the left and right side
walls 238, 239 of the sensing structure 215. The driving structure
225 includes first driving electrodes 242 that are disposed on a
bottom surface 246 of the driving structure 225. The first driving
electrodes 242 are disposed adjacent and perpendicular to the first
sensing electrodes 232.
[0015] The bottom substrate 205 is disposed below a top substrate
202 and includes second sensing electrodes 234 and second driving
electrodes 244 that are disposed on a top surface 249 of the bottom
substrate 205 and below the first sensing electrodes 232 and the
first driving electrodes 242. The first and second sensing
electrodes 232, 234 and the first and second driving electrodes
242, 244 provide a capacitance signal based on the movement of the
sensing structure 215 and the driving structure 225, respectively.
The capacitance signal is generated based on the sensing structure
215 and driving structure 225 moving perpendicular to the second
sensing electrodes 234 and second driving electrodes 244 in the
horizontal direction 220 and vertical direction 230,
respectively.
[0016] The first sensing electrodes 232 between the driving
structure 225 and the outermost structure 210 provide electrostatic
force to move the driving structure 225 when certain voltage
pattern is applied. The second sensing electrodes 234 between the
sensing structure 215 and the bottom substrate 205 provide
capacitance signal when the sensing structure 215 is moving. As the
driving structure 225 moves at a certain velocity back and forth, a
Coriolis force generally appears when the whole gyroscope 200
rotates. The Coriolis force moves the sensing structure 215 since
the driving structure 225 is coupled to the sensing structure 215.
By capacitively detecting the sensing structure movement using the
sensing electrodes 232, 234, the rotational signal can be
detected.
[0017] The sensing structure 215 and driving structure 225 are
generally a mass-damping-spring system. The dynamic mode of the
sensing structure 215 and driving structure 225 can be
translational or rotational, which depends on the operational
principles. The driving and sensing mechanism may use two-phase,
three-phase or some other driving mechanism. The driving structure
225 generally moves to a certain velocity at a certain frequency.
The sensing structure 215 generally detects the signal of the
movement of the sensing structure 215. Alternatively or
additionally, the sensing structure 215 and the driving structure
225 of the gyroscope 200 can be a single sensing structure 215 and
a single driving structure 225 or a combination of identical or
different sensing structures 215 and a combination of identical or
different driving structures 225. In case of multiple sensing
structures 215 and the driving structures 225, they can be
independent, or coupled. The coupling mechanism may implement
electrostatic/mechanical methods.
[0018] When the gyroscope 200 is subjected to an angular velocity,
the Coriolis effect transfers energy from the driving structure 225
to the sensing structure 215. The response of the sensing structure
215 provides information about the resultant angular motion. The
efficiency of the energy transfer increases by matching the
frequencies of oscillation of the sensing structures 215 and the
driving structures 225. The frequencies of the sensing structures
215 and the driving structures 225 can be matched by removing some
mass from top surfaces 237, 247 of either the sensing structures
215 or the driving structures 225, respectively, or both. The mass
from the top surfaces 237, 247 can be removed to certain depth
using deep etch, which is described further in relation to FIG.
3.
[0019] FIG. 3 is a top view of yet another embodiment of a
gyroscope, such as that shown in FIG. 2, and is denoted generally
by reference numeral 300. The gyroscope 300 includes an outermost
structure 310 having an octagon shape. The gyroscope 300 further
includes first, second, third, and fourth driving structures
325A-D, and first, second, third and fourth sensing structures
315A-D, all of which are disposed within the outermost structure
310. The first and third driving structures 325A, C that are
disposed between the first and second sensing structures 315A, B
and the third and fourth sensing structures 315C, D, respectively.
The first and third driving structures 325A, C are disposed
adjacent to top wall 360 and bottom wall 370, respectively. The
first, second, third, and fourth sensing structures 315A-D are
disposed adjacent to diagonal sides 365A-D, respectively.
[0020] The second driving structure 325B and fourth driving
structure 325D are further disposed between the second and third
sensing structures 315B, C, and the fourth and first sensing
structures 315D, A, respectively. A center member 335 is disposed
between the sensing structures 315A-D and driving structures
325A-D. The diagonal sides 365A-D include female members 355A-D
that engage with the male members 345A-D using microbeams 350A-H,
respectively. The male members 345A-D extend diagonally towards the
female members 355A-D, respectively.
[0021] The first, second, third, and fourth sensing structures
315A-D include first, second, third, and fourth sensing electrodes
(not shown), respectively. The first, second, third, and fourth
sensing electrodes are aligned substantially diagonally from the
top left, top right, bottom right, and bottom left, respectively,
toward the center of the top substrate. The first sensing
electrodes are opposite from the third sensing electrodes and the
second sensing electrodes are opposite from the fourth sensing
electrodes.
[0022] The first, second, third, and fourth driving structures
325A-D include first, second, third, and fourth driving electrodes
(not shown) that aligned parallel to the top wall 360, right side
wall 340, bottom wall 370 and left side wall 330 of the outermost
structure 310, respectively. The fourth and second driving
structures 325D, B move in the X-axis direction, and the first and
third driving structures 325A, C move in the Y-axis direction. The
sensing structures 315A-D move rotationally and measure the
rotational rate about the Z-axis.
[0023] In this example, the performance of the gyroscope 300 can be
improved by removing mass from the top surface 237 of the sensing
structures 315A-D. However, there is a potential difficulty in
controlling the exact depth in removing mass using, for example,
deep etch, resulting in a variation of resonance frequencies of the
sensing structures 215 and a mismatch of the frequencies between
the sensing structures 315A-D and the driving structures
325A-D.
[0024] The frequency matching can be improved by removing mass from
the top surface 247 (FIG. 2) in each driving structures 325A-D at
certain mass removal areas 390A-D. Such mass removal areas 390A-D
are designed and arranged to be adjacent to the center member 335.
The amount of the area and the location of the area depend on the
device geometric parameters. Since the mass removal areas 390A-D in
the driving structures 325A-D are close to the center of the
gyroscope 300, the areas 390A-D potentially have little affect on
the rotational inertia of the sensing structures 315A-D and the
resonance frequency of the sensing structures 315A-D. However, the
mass removal areas 390A-D can change the frequencies of the driving
structures 325A-D such that the areas 390A-D facilitate matching
the driving and sensing frequencies to vary in the same rate as the
etching depth varies at the sensing structures 315A-D.
[0025] FIG. 4 is a flow diagram that illustrates an embodiment of a
method for making a gyroscope, such as that shown in FIG. 2, that
can compensate for frequency mismatch. Beginning with step 405, the
method 400 provides a top substrate 202 (FIG. 2) and a bottom
substrate 205 (FIG. 2). The top substrate 202 includes at least one
driving structure 225 and at least one sensing structure 215. At
step 410, a portion of the mass on the top surface 237 of the
sensing structure 215 is removed and can be accomplished at certain
mass removal areas 390 (FIG. 3). At step 415, the mass removal area
390 on the top surface 247 of the driving structure 225 is placed
close to the center of the gyroscope. At step 420, the frequency of
the driving structure 225 is changed to match the frequency of the
sensing structure 215 due to removing the mass at the mass removal
area 390 on the top surface 247 of the driving structure 225.
[0026] This description has been presented for purposes of
illustration and description. It is not intended to be exhaustive
or to limit the disclosure to the precise forms disclosed. Obvious
modifications or variations are possible in light of the above
teachings. The embodiments discussed, however, were chosen to
illustrate the principles of the disclosure, and its practical
application. The disclosure is thus intended to enable one of
ordinary skill in the art to use the disclosure, in various
embodiments and with various modifications, as is suited to the
particular use contemplated. All such modifications and variation
are within the scope of this disclosure, as determined by the
appended claims when interpreted in accordance with the breadth to
which they are fairly and legally entitled.
* * * * *